Yeah, there's always the blood magic thing. But this isn't at all magical. No mages needed. There has to be some way to verify that what we're doing isn't magic, assuming we ever get that far, but it'll still have a reputation problem.

And you're right, there could be more blood types in play here. Really hard to know. Some nonhuman species at home have blood pretty similar to humans, and some are really different. At home, it's mostly illegal to transfuse nonhuman blood into humans, for a variety of reasons, but we don't have other species that we can communicate with in a common language either.

The way we do blood typing at home, you don't need a microscope, though. It's. [A short pause.] To sum up a lot: you add a particular substance to a blood sample, and how the mixture reacts tells you what the blood type is. I'm not sure that Stephen and I have the knowledge or the resources to make the substances we'd need, though. Back home, it's something you can just buy.